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Network recovery
Conventional wisdom holds that network reliability is typically 3-9s (99.9%) on a LAN, and 2-9s
(99%) on a WAN. The leading causes of network failure are a WAN link failure, administrator
error, cable failure, issues that involve connecting new devices or services, and malicious
activity, including DoS attacks, worms, and viruses. Somewhere lower down on the list are
equipment failures. To achieve the highest levels of availability, it is important that a strong
change control policy and network management strategy be implemented.
There are numerous techniques for improving the reliability of data networks, including
spanning tree, self-healing routing protocols, network management, and change control. This
section discusses the following techniques:
Change control
Layer 2 mechanisms to increase reliability
Layer 3 availability mechanisms
Dial backup
Convergence times
Change control
Change control describes a process by which an organization can control non-emergency
network changes, and reduce the likelihood of administrator errors that cause network
disruption. It involves carefully planning for network changes (including back-out plans),
reviewing proposed changes, assessing risk, scheduling changes, notifying affected user
communities, and performing changes when they will be least disruptive. By implementing a
strict change control process, organizations can reduce the likelihood of administrator errors,
which are a major cause of network disruption, and increase the reliability of their networks.
Change control
contains more information on change control.
Issue 3.4.1 June 2005
351
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